A power semiconductor apparatus typified by a power transistor package or the like has a packaging structure in which a rear-surface electrode of a semiconductor device having semiconductor elements formed longitudinally (in a direction vertical to a circuit surface of a semiconductor substrate) and a die pad of a lead frame are connected by die bonding, a main-surface electrode and a control electrode on a circuit surface side are electrically connected to respective external connection leads, and the entirety of the semiconductor device, the entirety or part of the die pads and a part of the external conduction lead are molded with insulating resin.
In the conventional die bonding of a power semiconductor apparatus with large or intermediate capacity, the soft high-Pb-content solder having the reflow resistance of about 260° C. and small thermal stress load to the semiconductor device has been used as a joint material. However, lead is a chemical substance harmful to environment and the use thereof is restricted under chemical substance regulation of each country typified by RoHS (Restriction of Hazardous Substances). Although the high-Pb-content solder is exceptionally excluded from the banned substances at present, the early shift to the lead-free material has been demanded. Alternative materials of the high-Pb-content solder have been considered all over the world, but no material capable of being applied to a product has been found out yet.
As the candidates of the lead-free material, Zn (zinc) series solder (for example, Japanese Patent Application Laid-Open Publication No. 2006-159201 (Patent Document 1)), Sn (tin)-Sb (antimony) series high-temperature solder (for example, Japanese Patent Application Laid-Open Publication No. 2005-340267 (Patent Document 2)) and high-conductive silver paste of resin adhesion type (for example, Japanese Patent Application Laid-Open Publication No. 2006-59905 (Patent Document 3)) have been known, and silver-nanoparticle bonding material utilizing the low-temperature fusion reaction of nanoparticles has been considered recently.